Wireless charging, also known as Wireless Power Transfer (WPT), is a technology that enables a power source to transmit electromagnetic energy to an electrical load across a gap, without interconnecting cords. Two directions for WPT are radiative wireless charging, which transfers energy via, for example, radiating electromagnetic, ultrasound, or acoustic waves and non-radiative charging, which transfers energy via an oscillating electromagnetic field.
Wireless power transmission systems can include a power transmitter unit (PTU) and power receiver unit (PRU). The transmitter can include components to supply power to a transmitter resonator coil which is coupled to a receiver resonator coil in a receiver. The receiver can be coupled to one or more loads, such as those of a mobile electronic device, medical device, vehicle, etc. It can be beneficial to have some type of communication path between the receiver and the transmitter in order to conserve efficiency.